Catheter head for subcutaneous administration of an active substance

ABSTRACT

The present invention provides a catheter head including a cannula housing, a needle holder connectable to the cannula housing and a guide sleeve associated with the needle holder for positioning and guiding a connecting needle, and for being narrowly slide-guided over a portion of said cannula housing.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part application of U.S.application Ser. No. 09/311,022, filed on May 13, 1999, which claims thepriority from German Patent Application No. 198 21 723.4, filed May 14,1998, both of which are incorporated herein by reference in theirentirety.

BACKGROUND

[0002] The invention relates to a catheter head for subcutaneousadministration of substances, including medically active substances,such as insulin and the like.

[0003] A catheter head as known from U.S. Pat. No. 5,522,803 comprises acannula housing with a cannula and a needle holder, to be connected tothe cannula housing, including a feed line for feeding a substance tothe catheter head. The cannula projects from the cannula housing and isplaced in tissue. In the cannula housing a passage channel to thecannula is formed for the active substance. The cannula housing isdesigned to allow flush, conforming or mould (or molded) positioning onthe surface of the tissue into which the cannula is placed, and it isprepared for being fixed on or attached to the tissue.

[0004] A connecting needle is rigidly attached to the needle holder. Theconnecting needle is introduced into the passage channel of the cannulahousing for obtaining a connection. Both the cannula and the cannulahousing will stay on the site of attachment in and on the tissue,whereas the needle holder may be repeatedly connected to the cannulahousing and separated from the same again. During assembly, the cannulahousing and the needle holder are automatically engaging into eachother, due to the needle holder detachably anchoring itself to thecannula housing. Guide means are provided for positioning the connectingneedle in relation to the passage channel of the cannula housing and forintroducing the connecting needle into the passage channel, with theguide means guiding the needle holder at the cannula housing.

[0005] The guide means of this known catheter head are formed by a pairof guide pins projecting on either side of the connecting needle andparallel to the same from the needle holder. Accordingly, the cannulahousing is provided with guide shafts on either side of an inlet intothe passage channel into which one each of the guide pins forintroducing the connecting needle is inserted. The connecting needle ispositioned in relation to the inlet by the interaction of the guide pinswith the guide shafts and guided in centered position duringintroduction into the passage channel. In the course of advancement ofthe connecting needle in the passage channel, the needle holder isanchored by an automatically engaging snap-on connection to the cannulahousing.

SUMMARY

[0006] It is an object of the invention to provide a catheter head forsubcutaneous administration of a substance comprising a cannula housingand needle holder which may be simply and correctly connected to eachother, and which is easy to manufacture.

[0007] In one embodiment, the present invention provides a catheter headcomprising a cannula housing, a needle holder connectable to the cannulahousing and a guide sleeve associated with the needle holder forpositioning and guiding a connecting needle, and for being narrowlyslide-guided over a portion of said cannula housing.

[0008] In one embodiment, the present invention comprises a housing witha cavity adapted to receive a soft cannula, an O-ring sealing gasket anda center part. The cavity is open at its upstream end and, at itsdownstream end, provides an annular seat around an opening. The softcannula includes one end with a radially outwardly extending flange. Thecenter part is shaped to fit generally closely within the cavity and,when placed in the cavity, is generally adjacent to the downstream end.The present invention encompases a method of assembling the housing,cannula, O-ring and center part of the present invention, wherein thecannula is positioned in the housing so that the flange is in contactwith the annular seat. The O-ring is placed in the cavity overlying theflange. The center part is inserted into the cavity from the upstreamend to the extent that it contacts and compresses the O-ring. The centerpart is then attached to the housing by, for example, ultrasonicallywelding it to the housing.

[0009] In one embodiment, the present invention provides a catheter headfor subcutaneous administration of a substance, comprising a cannulahousing carrying a soft cannula to be placed in tissue and having apassage to said cannula for the substance, the cannula housingcomprising an underside for flush positioning on a tissue surface, acenter part placed in and rigidly bonded with the cannula housing, and asealing device (e.g., a gasket, O-ring, packing, seal or the like)placed between a flange of the cannula and the center part.

[0010] In one embodiment the catheter head to which the inventionrelates comprises a cannula housing with a cannula and a needle holder,to be connected to the cannula housing, including a feed line forfeeding an active substance to the catheter head. The cannula projectsfrom within the cannula housing and is placed in tissue. The cannula maybe an integral part of the cannula housing or it can be retained withinthe cavity by a retaining body. In another embodiment, the cannula maybe attached and/or anchored inside the cannula housing. It may bedesigned as a rigid element, such as a steel cannula, or it may beflexible, or pliable. In the cannula housing a passage channel to thecannula is formed for the active substance. The cannula housing isdesigned to allow flush positioning on the tissue, into which thecannula is placed, and it is prepared for being fixed on to the tissue.

[0011] A connecting needle is rigidly attached to the needle holder. Theconnecting needle is introduced into the passage channel of the cannulahousing for obtaining a connection. Both the cannula and the cannulahousing will stay on the site of attachment in and on the tissue,whereas the needle holder may be repeatedly connected to the cannulahousing and separated from the same again. During connection orassembly, the cannula housing and the needle holder are preferablyautomatically engaging with each other, in particular due to the needleholder being detachably anchored to the cannula housing. Guide means areprovided for positioning the connecting needle in relation to thepassage channel of the cannula housing and for introducing theconnecting needle into the passage channel, with the guide means guidingthe needle holder at the cannula housing.

[0012] According to the invention, the guide means of the needle holderis a guide sleeve axially surrounding the connecting needle, said guidesleeve being pushed narrowly slide-guided over a cylindrical extensionof the cannula housing upon the needle holder and the cannula housingbeing connected, i.e. upon the connecting needle being introduced. Thecylindrical extension surrounds the inlet and a section of the passagechannel of the cannula housing connected to the same. The inventionensures secure introduction of the connecting needle without the need offorming additional guide pins. In addition, the guide sleeve representsa means of protection for handling, both for the needle and the user.The guide sleeve may have openings, but is preferably designed as aclosed sleeve body.

[0013] In one preferred embodiment, the cannula housing comprises acompact front section, from the underside of which the cannula projectsand from the rear of which a disc-shaped section and the cylindricalextension project, the disc-shaped section extending the underside ofthe cannula housing placed on the tissue. An upper side of thedisc-shaped rear section of the cannula housing facing the cylindricalextension and an underside of the needle holder are acting as additionalguide means upon the cannula housing and the needle holder are beingconnected, preventing rotation of the needle holder in relation to thecannula housing around the longitudinal axis of the connecting needle.

[0014] Preferably, an additional passage is formed in the cannulahousing for a piercing needle for the cannula. When the cannula housingand the needle holder are connected, this passage points at an angle inrelation to the connecting needle. The passage channel for theconnecting needle leads into this additional passage which extends thepassage channel up to the cannula after the cannula has been placed andthe piercing needle retracted. Owing to the fact that a piercing needleneed not be retracted from the passage channel, into which theconnecting needle is introduced after placing the cannula and fixing thecannula housing, complete precharging of the catheter head up to thecannula, i.e. priming, is possible in the state of the cannula housingand the needle holder being connected.

[0015] In another embodiment, a flexible cannula extends the passagechannel, but flush. In a third embodiment, the cannula may be formed bythe piercing needle itself.

[0016] In one manufacturing process, the prefabricated cannula ismoulded into the cannula housing when injection-moulding the cannulahousing. For this purpose, a rear section of the cannula is preferablyprovided with a widened section or flange which is anchored in thecannula housing during injection. The cannula may be made of a softplastic material, in particular Teflon. A thermoplastic material may beused both as a material for the cannula housing and for the needleholder.

[0017] Other objects, features, embodiments and advantages of the deviceand method of the present invention will become more fully apparent andunderstood with reference to the following description and appendeddrawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 depicts the catheter head in accordance with the presentinvention in assembled condition,

[0019]FIG. 2 is an exploded view of the catheter head depicted in FIG.1, with components of the catheter head being shown individually andremoved from their assembled position,

[0020]FIG. 3 depicts the catheter head according to FIG. 2 prior toassembly,

[0021]FIG. 4 is a longitudinal section depicting the catheter headaccording to FIGS. 1 to 3 in assembled condition,

[0022]FIG. 5 depicts a second embodiment of a catheter head, and

[0023]FIG. 6 is a longitudinal section of the catheter head shown inFIG. 5.

[0024]FIG. 7 is a longitudinal section of an alternative catheter head.

[0025]FIG. 8 is a cross-sectional view of a portion of anotherembodiment of a cannula housing.

[0026]FIG. 9 is an enlarged cross-sectional view of the of the cannulahousing of FIG. 7, and includes a phantom line depicting that the centerpart of the present invention may comprise more than one piece.

DETAILED DESCRIPTION

[0027] The accompanying figures and this description depict and describeembodiments of the catheter head and methods of the present invention,and features and components thereof. With regard to means for fastening,mounting, attaching or connecting the components of the presentinvention to form the device as a whole, unless specifically describedotherwise, such means are intended to encompass conventional fastenerssuch as threaded connectors, snap rings, clamps such as screw clamps andthe like, rivets, toggles, pins and the like. Components may also beconnected by adhesives, glues, welding, ultrasonic welding, and frictionfitting or deformation, if appropriate. Unless specifically otherwisedisclosed or taught, materials for making components of the presentinvention may be selected from appropriate materials such as metal,metallic alloys, natural and manmade fibers, vinyls, plastics and thelike, and appropriate manufacturing or production methods includingcasting, extruding, molding and machining may be used.

[0028] Any references to front and back, right and left, top and bottomand upper and lower are intended for convenience of description, not tolimit the present invention or its components to any one positional orspacial orientation.

[0029]FIG. 1 shows a catheter head H comprising a cannula 1, extendingvertically from an underside of the catheter head. The cannula 1, madeof a soft plastic material, for example, Teflon, closely surrounds apiercing needle N, projecting through the catheter head H transversely,preferably vertically or perpendicularly, in relation to its generallyflat, level underside. The catheter head H of FIG. 1 forms the front endof a catheter 5, as marked in FIGS. 2 to 4. The catheter with thecatheter head H is set by the user himself, for instance a diabetic. Forthis purpose, the piercing needle N and the cannula 1 are insertedvertically under the skin into the tissue, and the underside of thecatheter head is positioned adjacent to and/or fixed or attached to theskin. Fixation is effected by means of a self-adhesive pad or plaster.In one embodiment, the pad may enlarge the underside surface of thecatheter head H available for adhesion. Should the underside as suchprovide an adhesive area of a sufficient size, provision of such anunderside will be sufficient as an adhesive area. After placing thecannula 1, the piercing needle N is retracted from the catheter head,with only the thin, flexible, pliable, cannula 1 remaining in thetissue.

[0030] The catheter head H further comprises a cannula housing 2, whichremains at the point of piercing of the skin together with the cannula1, with an underside for fixing the catheter head to the skin, and aneedle holder 3, forming one front end of the catheter 5. The cannulahousing 2 and the needle holder 3 are combined in a plug-in connectionthat may be repeatedly connected and disconnected.

[0031] In FIG. 2, the cannula housing 2 and the needle holder 3 areshown detached or separated from each other, but aligned in relation toeach other for being coupled or plugged together. Furthermore, thecomponents of the catheter head H to be manufactured separately havebeen shown separated from their installed positions. All individualcomponents have been aligned in relation to each other in accordancewith their installation positions.

[0032] In use, an active substance is fed to the needle holder 3 throughthe catheter 5. It is passed through a connecting needle 4 within theneedle holder 3 into a passage channel in the cannula housing 2, then tothe cannula 1 and through the cannula 1 to the specified site into theissue. The piercing needle N shown in FIGS. 1 to 4 has been previouslyremoved. An inlet 9 and an adjacent section of the passage channel ofthe cannula housing 2 are surrounded by a cylindrical extension 6,projecting from a rear side of the cannula housing 2. The passage withinthe catheter head H can be best seen in detail from the longitudinalsection of FIG. 4.

[0033]FIG. 3 shows the cannula housing 2 and the needle holder 3 withthe individual components at their sites, each also arranged forassembly in a suitable position in relation to each other. From thisposition, the needle holder 3 is advanced in a straight line inlongitudinal direction of the connecting needle 4, pointing towards theinlet 9, towards the cannula housing 2 and attached. The feed andattaching direction of the needle holder 3 extends generally parallel tothe skin surface. The catheter is therefore leading away parallel to theskin surface, however, in some embodiments it may point away in an angleto the skin surface.

[0034] In assembled condition, the overall shape of the catheter head His a semi-ovaloid, comprising a generally level underside 12. While theunderside 12 is generally level or planar, in some embodiments it may becurved towards its edge, descending from the skin and ending in an upperside above, being in part convex and in part concave. The cannulahousing 2, on which the underside 12 placed on the skin is formed,comprises a rear disc-shaped section 11 and a front section 10 thickenedin relation to the same, from the underside 12 of which the cannula 1and from the rear of which the cylindrical extension 6 and, facing thesame, the disc-shaped section 11 project towards the rear into thedirection of the needle holder 3, to be advanced towards the same. Theupper side 13 of the rear section 11 is concave and rounded in shape,adapted to cooperate or compliment the curved underside 14 of the needleholder 3, being curved accordingly outwards. In contrast, the upper sideof the front section 10 is curved convexly outwards. The needle holder 3is of a symmetrical shape, i.e., its upper side and underside 14 areidentically curved outwards. In addition, the needle holder 3 issymmetrical in plan view in relation to its central axis. The undersideand the upper side of the needle holder 3 may be exchanged due to theirsymmetry when being plugged together with the cannula housing. Thissimplifies handling, due to correct alignment being verifiable easily bytouch alone.

[0035] During interaction with a guide sleeve 7 provided on the needleholder 3, the cylindrical extension 6 acts as a guide means forpositioning the connecting needle 4 in relation to the inlet 9 and forcorrect straight guidance of the connecting needle 4 within the sectionof the passage channel following the inlet 9. Thus, according to theinvention, a part of the cannula housing 2 surrounding the passagechannel, namely the cylindrical extension 6, is formed to project fromthe cannula housing 2 and allows to be used as a guide means forinserting the connecting needle 4. The guide means on the needle holder3, interacting with the same, is formed by the guide sleeve 7,simultaneously protecting the connecting needle 4, coaxially arranged inthe same, against damage. In addition, it protects the user againstpossible injury due to a projecting needle, for instance, when verifyingalignment by touch due to a lack of attention during handling. The guidesleeve 7 projects over the connecting needle 4 in its longitudinaldirection.

[0036] The guide sleeve 7 is formed by forming two longitudinal slots17, i.e., the sleeve 7 is between these two slots 17 as a sleeve-shapedextension. In principle, the guide sleeve 7 could be formed by theneedle holder 3 as a whole, i.e., being formed as a straight cylindricalrecess in an otherwise full needle holder 3, which would then beregarded in total as a guide sleeve.

[0037] However, two elastic snap-on fingers 16 are formed by the slots17 on either side of the guide sleeve 7, projecting over the guidesleeve 7. When attaching the needle holder 3, the snap-on fingers 16engage with appropriate guide shafts 15, provided on either side of thecylindrical extension 6 in the cannula housing 2. During the insertionor joining of the connecting needle 4, the snap-on fingers 16 slide overguide faces of their guide shafts 15 tapered towards each other and arebent by the same towards each other. The elastically bendable snap-onfingers 16 are snapped out by their engaging tabs behind projectionsformed in the guide shafts 15 upon the connecting needle 4 having beencompletely inserted, thus anchoring the needle holder 3 at the cannulahousing 2 by gripping behind the appropriate projections of the guideshafts. The snap-on connection is released by pressing the snap-onfingers 16 towards each other in their knurled sections. After havingreleased the grip from behind in this way, the needle holder 3 may beretracted from the cannula housing 2.

[0038]FIG. 4 is a longitudinal section of the catheter head. The guidesleeve 7 is completely pushed over the cylindrical extension 6, with itsfront edge contacting the rear of the cannula housing 2, from which thecylindrical extension 6 projects. In this condition, the snap-on fingers16 grip behind the appropriate tabs in the guide shafts 15. Thereforeaccidental release of the needle holder 3 is not possible.

[0039] When attaching the needle holder 3, the underside 14 of theneedle holder 3 slides along the curved upper side 13 of the cannulahousing 2. The guide sleeve 7 is positioned flush with the cylindricalextension 6 for positioning the connecting needle 4, wherein the needleholder 3 is displacable while being supported on the upper side 13 ofthe cannula housing 2. The cylindrical extension 6 is centered in theguide sleeve 7 when first being pushed over the cylindrical extension 6,due to the front edge of the cylindrical extension 6 being slightlyrounded. Thereafter, the needle holder 3 is pushed forward over thecylindrical extension 6 with its guide sleeve 7, whereby the connectingneedle 4 pierces a septum 8 directly arranged behind the inlet 9 in thepassage channel of the cylindrical extension 6. The septum 8 is designedto hermetically seal the passage channel of the cannula housing 2 evenafter repeatedly being pierced. Directly behind the septum 8, thepassage channel is provided with a domed section 18 into which theconnecting needle 4 projects. A straight channel section 19, leadinginto a cavity 20 in the front section 10 of the cannula housing 2,arranged flush with the connecting needle 4, follows the domed section18. The cannula 1, too, ends in the said cavity 20. The piercing needleN projects through the cavity forming, in this embodiment, a right angleto the connecting needle 4 and the channel section 19. The piercingneedle N projects through the cannula housing 2, extending in an angle,in this embodiment, in a right angle to its underside 12. In thisarrangement, the piercing needle N is advantageoulsy not guided throughthat part of the passage channel of the cannula housing 2 into which theconnecting needle 4 is introduced. In this arrangement, the piercingneedle N need not be removed in order to be able to introduce theconnecting needle into the cannula housing. This is advantageous forso-called “priming,” during which the catheter head H is being filled asfar as possible completely with the active substance prior to placingthe cannula 1. This considerably simplifies handling.

[0040] The cannula 1 is designed as a thin tube, comprising aflange-type widened section 21 at one end. The flange-type widenedsection 21 is placed in a disc-shaped recess of the cannula housing 2,thus anchoring the cannula 1.

[0041] Another septum 22 is inserted opposite the cannula inlet in thecavity 20, sealing the cavity 20, which forms part of the passagechannel of the cannula housing 2, after retracting the piercing needleN. The function of the septum 22 is comparable with that of the septum8. The shape of the cavity 20 is mainly cylindrical, with theflange-type widened section 21 of the cannula 1 and the septum 22forming the opposite faces of the cylindrical cavity 20, between whichthe channel section 19 ends. For priming, the piercing needle Ncomprises an opening in its section located between the flange-typewidened section 21 and the septum 22.

[0042]FIG. 4 clearly shows the flush support of the needle holder 3 overthe full surface of the upper side 13 of the disc-shaped rear section 11of the cannula housing 2. In addition, it is shown that a clearanceremains between the upper side 13 and the cylindrical extension 6 intowhich the guide sleeve 7 enters upon the needle holder 3 beingplugged-on. In principle, the said clearance between the disc-shapedsection 11 and the cylindrical extension 6 is not required. Thecylindrical extension 6 could, for instance, be located flat directly onthe disc-shaped section 11. In this design, the underside of the guidesleeve 7 would be suitably open. The internal jacket face, being theactual slideway (or race-like guiding and supporting structure or travelpath) for the guide sleeve 7 and the external jacket face of thecylindrical extension 6, need not be straight and circular orcylindrical in shape, although this is preferred, as long as sufficientslideway faces are available for positioning and neatly guiding theconnecting needle 4. Guidance and security of the needle holder 3against rotation in relation to the fixed cannula housing 2 is improvedby the upper side 13 of the cannula housing 2 and the underside 14 ofthe needle holder 3 acting as slideways. The shape of these two guidefaces 13 and 14 ensures correct alignment, in particular centering,during assembly.

[0043]FIGS. 5 and 6 show a modified embodiment, in which the piercingneedle is pierced through the same passage channel of the cannulahousing 2 into which the connecting needle 4 is to be inserted afterplacing the cannula 1. With the exception of the arrangement of thepiercing needle and the cannula 1, the catheter heads of FIGS. 5 and 6correspond to the arrangement described above. Reference is thereforemade to that description.

[0044]FIGS. 7 and 8 show alternative embodiments of a cannula housing 2which includes a generally cylindrical stepped cavity 31 extendingthrough the cannula housing 2, a cannula 32 extending from the cavity31, and a retaining body 33. In these embodiments, the cannula 32 is notcontiguous with the cannula housing 2 and is retained within the cavity33.

[0045] The cavity 31 defines an interior surface 34 which includes anannular seat 35 and an annular ledge 36. The cavity is generallycylindrical, and is of sufficient diameter to enable easy insertion ofthe cannula 32 and the retaining body 33. The passage 19 extends to thecavity 31 and is in communication thereto.

[0046] The cannula 32 is disposed within the cavity 31 with its lumenand central axis generally aligned with the central axis of the cavity.At one end, the cannula 32 includes a flange 37 extending radially fromthe cannula 32, which engages the seat 35 to position the cannula in thecavity and to limit axial movement of the cannula 32 within the cavity31. As explained more fully below, the flange 37 also plays a role insealing the assembled housing, cannula and center part. As shown in theembodiment of FIG. 8, the cannula 32, and/or cannula flange 37, may alsoinclude a generally frusto-conical seat area 38 for receiving a portionof the retaining body 33. It should be appreciated that this seat area38 may be preformed at the circumference of the lumen of the cannula 32or it may be formed by the compressive force generated or executed bythe retaining body 33 as it is being inserted and positioned in thecavity 31.

[0047] The retaining body 33 includes a retaining flange 39, a generallycentral through channel or passage 45, and a sealing surface 41. Theretaining flange 39 cooperates with the ledge 36 to help position andlimit relative axial movement of the retaining body 33 within the cavity31, e.g., to help correctly position it within the cavity and to helpdetermine that the selected amount of compressive force is applied tothe gasket 42. The channel 45 extends longitudinally and generallyaxially through the retaining body 33 and is substantially axiallyaligned with the lumen of the cannula 32 to allow for easy insertion andremoval of the piercing needle N. In the embodiment of FIG. 8, thesealing surface 41 defines a frusto-conical surface 40 designed to matewith and complement the frusto-conical seat 38. In the embodiments ofFIGS. 7 and 9, the retaining body 33 has a generally flat sealingsurface 41, whereby a gasket 42 is compressed between two substantiallyparallel separate sealing surfaces 41 and the upper surface of thecannula flange 32.

[0048] The sealing surface 41 cooperates with the gasket 42, which inone embodiment is an O-ring, and the cannula flange 37 to provide asubstantially impervious fluidic seal between the retaining body 33 andthe cannula 32 and between the cannula flange 37 and the seat 35 in thecannula housing 2. The retaining body 33 (which, as depicted in phantomin FIG. 9, may be comprised of two or more pieces) is positioned withinthe cavity 31 so that the sealing surface 41 provides a compressiveforce on the gasket which prevents the flange 37 and, a fortiori, thecannula 32, from movement, including axial movement, away from itsseated position within the cavity 31. In the embodiment of FIG. 8,sealing is provided by the frusto-conical surface 40 engaging thefrusto-conical seat 38.

[0049] The retaining body 33 is substantially rigidly secured to theinterior surface 34 of the cavity to prevent movement of the body 33relative to the cannula housing 2 after it is positioned therein.Preferably, the retaining body 33 is secured by ultrasonically weldingit to the interior surface of the cavity 31, but the use of a suitableadhesive, and/or the use of complimentary mating surfaces (e.g., threadsor textured surfaces) located on the retaining body 33 and interiorsurface 34 is also contemplated to secure and fix the body 33 to thehousing 2.

[0050] In some embodiments of methods of making the present invention,the cannula housing 2 may be produced in a single injection mouldingcycle. For this purpose, the prefabricated cannula 1 including itswidened section 21 and possibly the septum 8 and the septum 22, areinserted into the injection moulding tool and directly moulded into thesame as an integral part of the cannula housing 2. The requiredattachments in the shape of all-round shoulders surrounding theafore-mentioned components, are specified by the injection mouldingtool. The septums 8 and 22 may also be inserted into the cannula housing2, whereby the cannula housing 2 is remoulded in another productioncycle for retaining the septums 8 and 22. Moulding the cannula 1 inparticular is a considerable simplification of the process formanufacturing the cannula housing 2.

[0051] The foregoing description of the present invention has beenpresented for the purpose of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Modifications or variations are possible in light of theabove teachings. The embodiments were chosen and described to provide anillustration of the principals of the invention and their practicalapplication, and to enable one of ordinary skill in the art to utilizethe invention in various embodiments and with various modifications asare suited to the particular use contemplated. All such modificationsand variations are within the scope of the invention as determined bythe appended claims when interpreted in accordance with the breadth towhich they are fairly, legally, and equitably entitled.

What is claimed is:
 1. A catheter head comprising: a housing having acavity extending therethrough, the cavity defining a seat; a cannulaextending from within the cavity, the cannula having a flange extendingtherefrom; a retaining body secured to the housing, the retaining bodyhaving a pathway extending axially therethrough and defining a sealingsurface; and a gasket in sealing cooperation with the flange and thesealing surface.
 2. The catheter head of claim 1 , wherein the retainingbody is ultrasonically welded to the housing.
 3. The catheter head ofclaim 2 , wherein the gasket is an O-ring.
 4. The catheter head of claim1 , wherein the sealing surface is frusto-conical.
 5. The catheter headof claim 4 , wherein the cannula includes a frusto-conical seat whichreceives a portion of the sealing surface.
 6. The catheter head of claim1 , wherein the cavity defines a ledge and the retaining body includes aflange which cooperates with the ledge to limit axial movement of theretaining body within the cavity.
 7. The catheter head of claim 1 , andfurther comprising a passage in communication with, and extendingradially from, the cavity.
 8. The catheter head of claim 1 , and furthercomprising a piercing needle extending through the cavity, the retainingbody, and the cannula.
 9. A catheter head comprising: a cannula housinghaving a cavity extending therethrough defining an internal surface anda passage in communication with the cavity; a cannula extending from thecavity, the cannula having a flange extending radially therefrom; aretaining body secured within the cavity and in cooperation with theinternal surface to locate the flange within the cavity; a needle holdercomprising a guide sleeve axially surrounding a connecting needle; and aguide extending from the cannula housing and cooperating with the guidesleeve to position the connecting needle into the passage.
 10. Thecatheter head of claim 9 , wherein the guide sleeve comprises a closedjacket surface surrounding the connecting needle.
 11. The catheter headof claim 9 , wherein an upper side of the cannula housing forms, duringinsertion of the connecting needle into the passage, a support and anadditional slideway for the needle holder.
 12. The catheter head ofclaim 11 , wherein the upper side is adapted to an underside of theneedle holder which is curved in cross direction to said connectingneedle, the upper side thus forming said additional slideway.
 13. Thecatheter head of claim 9 , wherein an underside of the needle holder ismould positioned on an upper side of a rear section of the cannulahousing during positioning and insertion of the connection needle. 14.The catheter head of claim 9 , wherein the needle holder comprises anupper side symmetrical to its underside, wherein the underside and theupper side are preferably curving outwardly away from each other. 15.The catheter head of claim 9 , wherein a piercing needle for saidcannula projects through the cannula housing at an angle to thelongitudinal direction of the inserted connecting needle.
 16. Thecatheter head of claim 9 , wherein the cannula includes a frusto-conicalseat which receives a portion of the retaining body.
 17. The catheterhead of claim 9 , wherein the retaining body includes a frusto-conicalsealing surface.
 18. The catheter head of claim 9 , and furthercomprising an O-ring disposed between the retaining body and the flange.19. The catheter head of claim 9 , wherein the retaining body isultrasonically welded to the interior surface.
 20. The catheter head ofclaim 9 , wherein the cavity defines a ledge and the retaining bodyincludes a flange which cooperates with the ledge to limit axialmovement of the retaining body within the cavity.
 21. A catheter headfor subcutaneous administration of a substance, comprising: a cannulahousing carrying a soft cannula to be placed in tissue and having apassage to said cannula for the substance; a center part placed in andrigidly bonded to the cannula housing; and means for sealing between aflange of the cannula and the center part.
 22. The catheter head ofclaim 21 , wherein the cannula housing comprises an underside for flushpositioning on a tissue surface.
 23. The catheter head of claim 21 ,wherein the means for sealing comprises an O-ring.
 24. A catheter headcomprising: a housing with a cavity, wherein the cavity has an openingand an annular seat around the opening, a soft cannula having a portionin contact with the annular seat; means for sealing; and a center partreceived in the cavity, whereby the means for sealing is lodged betweenthe portion of the cannula and the center part.
 25. The catheter head ofclaim 24 , wherein the center part is shaped to fit generally closelywithin the cavity.
 26. The catheter head of claim 25 , wherein theportion of the cannula comprises a radially outwardly extending flange.27. The catheter head of claim 26 , wherein the center part comprises asingle piece.
 28. A method of assembling a catheter head comprising ahousing having a cavity with a seat, a cannula with a flange, an O-ringand a center part, said method comprising the steps of: positioning thecannula in the cavity so the flange is in contact with the seat; placingthe O-ring in the cavity overlying the flange; placing the center partin the cavity to the extent that it contacts and compresses the O-ring;and attaching center part to the housing.
 29. The method according toclaim 28 , wherein said attaching is accomplished by ultrasonicallywelding the center part to the housing.